introduce rb_nogvl C-API to mark ubf as async-signal-safe

zlib and bignum both contain unblocking functions which are
async-signal-safe and do not require spawning additional
threads.

We can execute those functions directly in signal handlers
without incurring overhead of extra threads, so provide C-API
users the ability to deal with that.  Other C-API users may
have similar need.

This flexible API can supercede existing uses of
rb_thread_call_without_gvl and rb_thread_call_without_gvl2 by
introducing a flags argument to control behavior.

Note: this API is NOT finalized.  It needs approval from other
committers.  I prefer shorter name than previous
rb_thread_call_without_gvl* functions because my eyes requires
big fonts.

[Bug #15499]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66712 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 3 insertions, 0 deletions

diff --git a/vm_core.h b/vm_core.h
index ea59e417ef..7852ca4625 100644
--- a/vm_core.h
+++ b/vm_core.h
@@ -608,6 +608,9 @@ typedef struct rb_vm_struct {
     VALUE thgroup_default;
     int living_thread_num;
 
+    /* set in single-threaded processes only: */
+    volatile int ubf_async_safe;
+
     unsigned int running: 1;
     unsigned int thread_abort_on_exception: 1;
     unsigned int thread_report_on_exception: 1;